To investigate the effect of preparation methods on surface characteristics and adsorption properties of the formed metal composite oxides, two kinds of iron-titanium binary oxides were synthesized by a coprecipitation method or a physical mixing method and were denoted as CFe-Ti and MFe-Ti, respectively. The prepared CFe-Ti and MFe-Ti were systematically characterized using SEM, XRD, BET, and FTIR techniques. Their phosphate adsorption behaviors were also studied via batch adsorption experiments. Compared with pure FeOOH and TiO2, CFe-Ti exhibited a looser nanostructure with more pore and surface hydroxyls. Moreover, the CFe-Ti had a high maximal phosphorus adsorption capacity of 40.6 mg·g-1, which is about 1.5 times and 2.4 times as high as that of pure FeOOH (27.2 mg·g-1) and TiO2 (16.7 mg·g-1), respectively. This suggests that an obvious synergistic effect is present in the CFe-Ti system. However, the morphology and structure of MFe-Ti were not significantly different from those of pure FeOOH and TiO2. The maximal adsorption capacity of MFe-Ti was 22.7 mg·g-1, which is obviously lower than that of CFe-Ti and even lower than that of pure FeOOH. Evidently, there is no synergistic effect in the MFe-Ti system. In addition, phosphate adsorption mechanisms at the surface of CFe-Ti and MFe-Ti were the same as those of their component oxides, and chemical adsorption occurred at the surface of the oxides through the formation of inner-sphere complexes. Therefore, the surface characteristics and adsorption properties of the metal composite oxides were closely related to their preparation methods. The coprecipitation method was a simpler and more economical way than the physical mixing method to fabricate a highly effective iron-titanium binary oxide for phosphate adsorption.
Keywords: adsorption; coprecipitation; iron-titanium binary oxide; phosphate; physical mixing.